Ultrasonic borescope for drilled shaft inspection

ABSTRACT

A borescope includes a housing extending from a first end toward a second end, the housing including a first transparent viewing section extending circumferentially around a longitudinal axis of the housing and defining an exterior of a portion of the housing; a first imaging assembly configured to rotate about the longitudinal axis of the housing, and also pivot relative to the longitudinal axis of the housing; and a second imaging assembly disposed within the housing, the second imaging assembly being configured to rotate about the longitudinal axis of the housing, wherein the second imaging assembly is configured to visualize a field of view exterior of the housing through the first transparent viewing section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. 119 ofU.S. Provisional Patent Application No. 62/575,822, filed on Oct. 23,2017, which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The disclosure relates generally to a borescope system for use ininspecting and profiling drilled shafts, also referred to as bores orboreholes, using multiple cameras and ultrasonic sensors. In particular,the disclosure relates to a portable system for inspecting and profilingrelatively large drilled construction shafts that may improve inspectionefficiency in terms of maneuverability, information gathering, datarecording, data analyzing, and data qualifying.

INTRODUCTION

Drilled construction shafts that are subsequently filled with concreteor similar materials provide support for many large building andinfrastructure projects. For this reason, field engineers, andinspectors involved in preparing such shafts are particularly concernedwith ensuring that the load transfers in side resistance and in endbearing are consistent with any assumptions made during the designphase.

Normally, project design methods assume that drilled shafts areconstructed under competent supervision with ample quality control andthe finished foundation will be durable and have structural integrity.However, such assumptions are not always warranted. For example, thefoundation boreholes constructed are roughly cylindrical in shape.However, the theoretical volume of bore is not same as the actual volumeof the bore due to reasons such as hole size being greater than the bitused to create the hole, caving on the side of the bore, etc. Unlessproject specifications and procedures are closely followed in the field,for example, the final shaft may have defects that can influence itsstructural and bearing capacity when filled. Therefore, the inspectionand profiling of the drilled shafts and the record keeping associatedwith the shaft construction are important and require careful attention.

Defects of a finished support structure and the conditions under whichsuch defects occur may involve a number of causes. For example, defectstypically result from one or more of the following: 1) over stressingthe soil beneath the shaft base due to insufficient bearing (contact)area or because of unconsolidated materials located at the shaft base;2) excessive mixing from mineral slurry, which can affect thedevelopment of concrete strength and/or formation of voids and cavitieswithin the set concrete; and 3) structural discontinuities and/ordeviations from the true vertical line causing local, undesirable stressconcentrations. In general, these and other defects can result ininsufficient load transfer reducing the bearing capacity of the finalstructure and/or causing excessive settling during service.

To develop the required end bearing capacity, the drilled shaft shouldbe inspected so that undesirable debris may be removed prior to concreteplacement. Shaft failures have been attributed to insufficient boreholecleaning, and cleaning the base of boreholes often require specialtools. Although the operation sounds simple, a typical cleaning processinvolves several steps including visually inspecting the borehole,sounding the base of the shaft by a weight attached to a chain, andobtaining samples of the side walls and the base. Based on the resultsof the visual, sounding, and sampling inspections, a trained inspectordetermines whether the borehole must be cleaned or otherwise alteredbefore concrete placement. The inspector usually bases his or herdecision on the condition of the borehole and the amount of sedimentarydeposits at the base. If the inspector determines that cleaning iswarranted, several methods may be used, including air lifting, using aclean-out-bucket, or removing debris and unwanted material with asubmerged pump.

SUMMARY

In one aspect, the disclosure is directed to a borescope that mayinclude a housing extending from a first end toward a second end, thehousing including a first transparent viewing section extendingcircumferentially around a longitudinal axis of the housing and definingan exterior of a portion of the housing; a first imaging assemblyconfigured to rotate about the longitudinal axis of the housing, andalso pivot relative to the longitudinal axis of the housing; and asecond imaging assembly disposed within the housing, the second imagingassembly being configured to rotate about the longitudinal axis of thehousing, wherein the second imaging assembly is configured to visualizea field of view exterior of the housing through the first transparentviewing section.

A shaft may extend at least partially through the housing, wherein thefirst imaging assembly and the second imaging assembly are bothconfigured to rotate simultaneously about the longitudinal axis of thehousing by rotation of the shaft. The borescope may include atransparent observation chamber having a first end disposed at oradjacent to the second end of the housing, and extending away from boththe first end and the second end of the housing, toward a second end.The second end of the housing may be configured to transition between aclosed configuration where an exterior of the observation chamber formsa fluid-tight seal around a volume, and an open configuration wherefluid can move into and out of the observation chamber through thesecond end. The borescope may include one or more rods at or adjacent tothe second end of the housing, wherein: each of the one or more rodsextends from the second end of the housing and away from both the firstend and the second end of the housing; and each of the one or more rodsincludes a plurality of graduated markings forming a scale indicative oflength, wherein each scale is visible to the first imaging assemblythrough the transparent observation chamber. The borescope may includean expandable sleeve coupled to an exterior of the housing, wherein theexpandable sleeve is configured to move from a collapsed position to anexpanded position via application of a fluid through the sleeve. Theborescope may include a rigid support at a radially outermost portion ofthe expandable sleeve, the rigid support enclosing an opening throughwhich the fluid can exit the expandable sleeve, wherein the secondimaging assembly is configured to visualize a field of view exterior ofthe housing through the opening and the expandable sleeve. Theexpandable sleeve may be coupled to the exterior of the housing by atransparent frame disposed circumferentially around the housing. In theexpanded position, the expandable sleeve may extend only partiallyaround a circumference of the housing. The borescope may include anultrasonic sensor at or adjacent to the second end of the housing,wherein the ultrasonic sensor is configured to determine a thickness ofsediment disposed at a bottom of a borehole. The borescope may include afirst ultrasound sensor configured to generate ultrasound waves; and areflector movable toward and away from the first ultrasound sensor alongthe longitudinal axis, or along a first axis parallel to thelongitudinal axis, wherein the reflector is configured to reflect theultrasound waves generated by the first ultrasound back toward the firstultrasound sensor, and the first ultrasound sensor is configured todetermine a time-of-flight for a wave to travel from the firstultrasound sensor to the reflector, and then back to the firstultrasound sensor. The reflector may be movable between a fullycompressed position and a fully extended position. The reflector may bedisposed closer to the first ultrasound sensor when in the fullycompressed position than when in the fully extended position. Theborescope may include a biasing member configured to bias the reflectortoward the fully extended position. The borescope may include a rodhaving a first end and a second end, wherein the reflector is disposedat the first end of the rod; and a tapered block disposed at the secondend of the rod, wherein the tapered block tapers radially inward in adirection away from both the first end and the second end of thehousing. The borescope may include a second ultrasound sensor configuredto rotate about the longitudinal axis of the housing; and a controllerconfigured to receive measurements from the second ultrasound sensor todetermine a volume of a borehole in which the borescope is located. Theborescope may include a depth sensor configured to determine a depth ofthe borescope, wherein the controller is configured to receivemeasurements from the depth sensor, wherein determination of the volumeof the borehole also is based on the measurements from the depth sensor.

In another aspect, the disclosure is directed to a borescope that mayinclude a housing extending from a first end toward a second end; afirst imaging assembly coupled to the housing; a first ultrasound sensorconfigured to generate ultrasound waves; and a reflector movable towardand away from the first ultrasound sensor along a longitudinal axis,wherein the reflector is configured to reflect the ultrasound wavesgenerated by the first ultrasound back toward the first ultrasoundsensor, and the first ultrasound sensor is configured to determine atime-of-flight for a wave to travel from the first ultrasound sensor tothe reflector, and then back to the first ultrasound sensor.

The reflector may be movable between a fully compressed position and afully extended position. The reflector may be disposed closer to thefirst ultrasound sensor when in the fully compressed position than whenin the fully extended position. The borescope may include a biasingmember configured to bias the reflector toward the fully extendedposition. The borescope may include a rod having a first end and asecond end, wherein the reflector is disposed at the first end of therod; and a tapered block disposed at the second end of the rod, whereinthe tapered block tapers radially inward in a direction away from boththe first end and the second end of the housing.

In yet another aspect, the disclosure is directed to a borescope thatmay include a housing having extending from a first end toward a secondend; a first imaging assembly coupled to the housing; an ultrasoundsensor configured to rotate about a longitudinal axis of the housing;and a controller configured to receive measurements from the ultrasoundsensor to determine a volume of a borehole in which the borescope islocated.

The borescope may include a depth sensor configured to determine a depthof the borescope, wherein the controller is configured to receivemeasurements from the depth sensor, wherein determination of the volumeof the borehole also is based on the measurements from the depth sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a borescope system for visuallyinspecting and profiling drilled shafts according to an embodiment ofthe disclosure.

FIG. 2A is a side view of a measurement assembly of the system of FIG.

FIG. 2B is a cross-sectional view of the measurement assembly of FIG.2A, taken along line 2B-2B.

FIG. 2C is an end bottom view of the measurement assembly of FIG. 2A.

FIG. 3 is an exploded view of an ultrasonic penetrometer assembly andcamera assembly.

FIGS. 4A and 4B are exploded side views of the ultrasonic penetrometerassembly of FIG. 3.

FIG. 5 is a schematic view of the camera assembly of FIG. 3.

FIG. 6A is a cross-sectional view of a dual camera assembly according toanother embodiment of the disclosure.

FIG. 6B is an end view of a portion of the assembly of FIG. 6A.

FIG. 6C is a perspective view of the assembly of FIG. 6A.

FIG. 6D is an illustration of the assembly of FIG. 6A deployed in aborehole.

FIG. 7A is a schematic view of a profiling assembly inside a foundationbore.

FIG. 7B is a side view of the profiling assembly of FIG. 7A.

FIG. 7C is an example output developed for the assembly of FIG. 7A.

FIG. 8 is a block diagram of a borescope system for visually inspectingand profiling drilled shafts according to another embodiment of thedisclosure.

FIG. 9 is a schematic diagram of control circuitry for use with theborescope system of FIG. 8.

FIG. 10 is a schematic diagram of a load cell arrangement associatedwith the control circuitry of FIG. 9.

FIG. 11 is an illustration of multiple measuring assemblies deployed inseparate boreholes.

DETAILED DESCRIPTION

Embodiments of the disclosure provide, among other things, a system foraccurately inspecting and profiling relatively large constructionboreholes such as those prepared for building and various infrastructuredrilled shaft foundations. The disclosure may help provide an accuratevisual inspection and volume profile of boreholes to construct deepfoundations or slurry walls. Embodiments of the disclosure may determinethe strength and thickness of the materials at the bottom of a borehole,a volume of a borehole, the quality of rock surrounding a borehole, aswell as the physical and electrical properties, such as, the pressureand the temperature of the slurry in the borehole. This may beaccomplished by a portable system utilizing at least one camera andultrasonic sensors in a watertight assembly. The system of the presentdisclosure provides a device for full drilled shaft inspection that asingle user can operate.

In one embodiment, an inspection system of the disclosure collects datain analog and/or digital form and is capable of providing digitalinformation to a computing device using a cable. In yet anotherembodiment, the camera and ultrasonic sensors are controlled wirelesslyfrom a computing device. Thus, it is economical and convenient in termsof the number of required personnel and efficient in storing andretrieving the needed information.

The present disclosure may be particularly well-suited for inspection inwaterways projects and may provide clear vision in environments wherevisibility is limited. Moreover, the features of the present disclosuredescribed herein may be less laborious and easier to implement thancurrently available techniques, as well as being economically feasibleand commercially practical.

Referring now to the drawings, FIG. 1 illustrates a borescope system inblock diagram form. As shown, the system includes a measurement assembly100 connected to a display 110 (e.g., a relatively small, portable videodisplay or television) for visually inspecting a borehole. A typicalborehole is several feet in diameter (e.g., about nine feet) and has aneven greater depth (e.g., about 150 feet). It is to be understood,however, that a borehole describes any opening in the ground that haseither a generally cylindrical geometry of a few inches to several feetin diameter and depth or a generally rectangular cutoff wall in theground with a few inches to several feet in width/depth. Drillers maysink a borehole using a drilling rig or a hand-operated rig. Themachinery and techniques to advance a borehole vary considerablyaccording to manufacturer, geological conditions, and the intendedpurpose. The borehole can be dry or wet (at least partially filled withtransparent, translucent, or opaque fluid). The borehole can be selfsupported, cased, or a pipe pile. The ratio of the size of the boreholeto the measurement assembly 100 can be about 1:1 (so long as the housingfits within the borehole), about 2:1, about 3:1, about 4:1, about 5:1,about 10:1, or about 28:1.

As described in detail below, the present system may be used to visuallyinspect boreholes to construct deep foundations or slurry walls using atleast one camera. In addition, the system may be able to determine thestrength and characteristics of the materials at the bottom of theboreholes, the volume of the borehole; and the physical and electricalproperties, the pressure, and the temperature of the slurry in theborehole.

According to embodiments of the disclosure, measurement assembly 100generates images and measurements of the interior surfaces of theborehole while suspended in the borehole. In one embodiment, theborescope system provides a line 114 to a computer 118 for displayingand recording the captured images and measurements. In the embodimentshown, measurement assembly 100 communicates with the computer 118 via apower-control cable 120 (also referred to as an umbilical cord).Measurement assembly 100 communicates with computer 118 according to,for example, an RS232 standard, although any other suitable mechanismalso is contemplated. It is to be understood that computer 118 may beused in addition to or instead of the display 110 and video recorder 112for recording the video images of the interior of the borehole andmeasurements of soil characteristics generated by measurement assembly100.

The borescope system of the disclosure also includes a case 130 forhousing, storing, and transporting various components of the system. Thecase 130 houses a rechargeable, or otherwise replaceable, battery 134for supplying power to the various components of the system. In someembodiments, duplicate power and battery systems may be incorporated. Anappropriately wired connector panel 136 may provide electricalconnections between the various components such as the battery 134,measurement assembly 100, display 110, and/or computer 118.

Although computer 118 is shown as a laptop computer in FIG. 1, othercomputer configurations are easily adapted for use with the presentdisclosure, including, for example, tablets (e.g., construction- ormilitary-grade tablets), smart phones, and the like. Moreover, computer118 may be self-powered (e.g., independently battery powered), receivepower from battery 134, or receive power from an external sourceindependent of the borescope system.

In the illustrated embodiment, battery 134 supplies power to display 110and recorder 112 via a display power connection 138 and a power line(not shown). Battery 134 also supplies power to measurement assembly 100via a camera input 140, an ultrasonic sensor input 144 and thepower-control cable 120. In the embodiment shown in FIG. 1, the line 114supplies camera data and sensor measurements to computer 118 (or anotherexternal monitor) via a video connector 142. The connector panel 136also includes a control input 146 described below.

As will be explained in greater detail below, a controller 150 controlsmeasurement assembly 100. The controller 150 is connected on one side,by an umbilical cord containing power-control cable 120 to computer 118.Controller 150 is connected on another side to control input 146 onconnector panel 136 via a cable or wireless communication. As shown inFIG. 1, controller 150 further includes a pan controller 152 and a tiltcontroller 154. Control signals generated by controllers 152, 154 aretransmitted to measurement assembly 100 via power-control cable 120.Additionally, the RS232 link between computer 118 and measurementassembly 100 is established via controller 150. Thus, it is possible togenerate and transmit computer controlled input information tomeasurement assembly 100 via controller 150. Likewise, computer 118 canreceive information pertaining to at least one camera or ultrasonicsensor from measurement assembly 100 via controller 150.

The connector panel 136 also provides access to a power supply fuse 156,as well as a system power switch 158 and a power indicator 160. Althoughit is anticipated that the borescope system will often operate using thebattery 134, the system also may be connected directly to an externalpower source using a power line (not shown) connected via a powerconnector 164. The external power line and power connector 164 also maybe used to recharge the battery 134 when the system is not being used.Although the embodiment shown in FIG. 1 contemplates the use of a 12volt power system, the borescope system of the present disclosure is inno way limited to 12 volt systems. Additionally, the case 130 alsoincludes at least one storage compartment 172 for storing variouscomponents of the borescope system when the system is not in use orbeing transported. A borescope system according to the disclosure maypermit control, measurement, and/or display of the depth of ultrasonicpenetrometer and camera assembly depth, and/or descending velocity aswell as electrical conductivity, pressure, thickness, and/or temperatureof the slurry contained in the borehole.

Measuring assembly 100 also may include a seismic source 180 and ageophone (or other suitable sensor) 182. Seismic source 180 may be anydevice that generates controlled seismic energy used to perform bothreflection and refraction seismic surveys. Seismic source 108 mayprovide single pulses or continuous sweeps of energy, generating seismicwaves, which travel through the ground. In one example, seismic source180 may be a hammer (e.g., a pneumatic hammer), which may strike a metalplate to generate the seismic waves. Some of the seismic waves generatedby seismic source 180 may reflect and refract, and may be recorded bygeophone 180.

Seismic source 180 and geophone 182 may be used to investigate shallowsubsoil structure, for engineering site characterization, or to studydeeper structures, or to map subsurface faults. The returning signalsfrom the subsurface structures may be detected by geophone 182 in knownlocations relative to the position of the subsurface structures.

As shown in FIG. 11, multiple measuring assemblies (e.g., assemblies 100a and 100 b) disposed in separate boreholes (e.g., 10 a and 10 b) can beequipped with a seismic source and geophone to provide additionalinformation regarding subsurface structures in a given area. Forexample, a seismic source 180 a may be activated to create seismic wavesdetectable by both a geophone 182 a on the same measuring assembly, aswell as being detectable by a geophone 182 b from a different measuringassembly located in a different borehole. Similarly, seismic source 182b may be activated to create seismic waves detectable by both geophone182 b and geophone 182 a.

Referring now to FIGS. 2A and 2B, measurement assembly 100 includes acamera 216 and an ultrasonic penetrometer 218. As described above, thesize of the borehole may be much larger than the size of the measurementassembly 100 (e.g., about 28 times or more). In one embodiment, thewidth of measurement assembly 100, including camera 216, issubstantially less than the diameter of the borehole under inspection(e.g., approximately ten inches compared to several feet). The center ofthe measurement assembly 100 may include a central axis 224. Camera 216and ultrasonic penetrometer 218 are positioned concentrically aboutcentral axis 224.

Camera 216 may be housed within an assembly 204. Assembly 204 isgenerally cylindrical in this embodiment and constructed using a rigidmaterial such as aluminum. It is to be understood, however, that othermaterials, such as polyvinyl chloride (PVC), may be suitable forprotecting camera 216. Observation chamber 206 provides camera 216 withviewing access to, e.g. a borehole, while protecting camera 216 fromdamage due to contact with the surfaces being inspected. Any suitabletransparent material, including, e.g., glass or transparent plasticcould be used to construct observation chamber 206.

Supporting or protective rods 214 are attached to assembly 204 andsurround observation chamber 206. Supporting rods 214 protect chamber206 when the system is lowered into a borehole. Supporting rods 214 maybe circumferentially spaced apart from one another about axis 224, andmay include graduated markings (indicative of length, e.g., a ruler)along their respective lengths. When measurement assembly 100 ispositioned at the bottom of a borehole, measurement assembly 100,including supporting rods 214, may sink into a soft material at thebottom of the borehole. When viewed by a camera 216, the markings ofsupporting rods 214 may help determine how far measurement assembly 100has sunk into the bottom of the borehole.

Observation chamber 206 is a generally cylindrical structure constructedof rigid, transparent plastic or a similar material, although othersuitable shapes are also contemplated. Observation chamber 206 may havea larger diameter than assembly 204. In an alternative embodiment,observation chamber 206 is made of a flexible, durable, transparentplastic. Observation chamber 206 is particularly well-suited for use inslurry-filled boreholes.

Boreholes are often filled with a viscous mud, or slurry, especially inwaterways projects. The slurry, however, obscures the view of the sidewalls and bottom of the filled borehole. Observation chamber 206provides camera 216 with a viewing interface. In operation, a systemoperator lowers camera 216 into observation chamber 206. According tothe disclosure, a fluid source 175 may supply pressurized air and/orwater (e.g., a gas and a liquid simultaneously) to the observationchamber 206 to push out slurry and mud from the space enclosed byobservation chamber 206 to provide clear view of the borehole bottom orside surface even though measurement assembly 100 is submerged in theslurry. Observation chamber 206 thus helps define a viewing area forcamera 216 in situations where a camera could not otherwise view thewalls or bottom of the borehole. By moving the viewpoint of camera 216in observation chamber 206, the operator may obtain images and videos ofthe borehole's interior surface. A light source (LED) may be located onthe side of observation chamber 206 e.g., on mounting brackets forcamera 216, to illuminate the viewing area while camera 216 is capturingimages and videos of the interior surface of the borehole. In someembodiments, observation chamber 206 may have a closed bottom end. Insuch an embodiment, measuring assembly 100 may be lowered into aborehole while flush with the inner circumferential surface of theborehole, to enable a user to view the inner circumferential surface.The closed bottom end may be achieved via a removable end cover toenable measuring assembly 100 to have multiple operating modes, e.g.,one mode with an open bottom end where fluid can move into and out ofobservation chamber 206, and another mode with a closed bottom end wherean exterior of observation chamber 206 forms a fluid tight seal aroundan interior volume of observation chamber 206.

Measuring assembly 100 also includes ultrasonic penetrometer 218 forsensing physical characteristics of the soil and bore. Ultrasonicpenetrometer 218 may be used to measure characteristics of soil such assediment thickness, calibrated resistance, and slurry density. Thepresent disclosure may be used to determine the structural adequacy of aborehole by capturing clear and accurate images (and videos) of theborehole's bottom and side surfaces. Cleanliness of the bottom and sidesof the borehole from any soil or rock residues is an important factorfor determining whether the borehole is adequate for constructing deepfoundations or slurry walls. Also, evaluating borehole adequacy mayinclude identifying cracking in pipe piles or defects in boreholecasing.

FIG. 2C depicts the bottom view of measurement assembly 100 showingultrasonic penetrometer 218 surrounded by the observation chamber 206and supporting rods 214. Ultrasonic penetrometer 218 may be displacedadjacent to the periphery of observation chamber 206 accordingly (shownin FIG. 2C), so the penetrometer 218 does not interfere with themovement or view area of camera 216. In such an embodiment, ultrasonicpenetrometer 218 may be offset from axis 224 and camera 216.

Referring back to FIG. 2B, a top cover assembly 202 connects to assembly204 on one side (shown in FIG. 2B) and to the control and display systemon the other side via power-control cable 120 (as shown in FIG. 1).Assembly 204, top cover assembly 202, observation chamber 206, andsupporting rods 214 are assembled to create a substantially watertightprotective housing for the electronics of measurement assembly 100.

FIG. 3 depicts an exploded side view of measurement assembly 100. Inparticular, FIG. 3 depicts an ultrasonic penetrometer 218 coupled toassembly 204, chamber 206, supporting rods 214, and camera assembly 316.The supporting rods 214 surround glass chamber 206 for protection ofultrasonic penetrometer 218 and camera assembly 316.

FIGS. 4A and 4B show ultrasonic penetrometer 218 including an ultrasonicsensor 438, a measurement scale 404, and a cone shaped protrusion(tapered block) 402. Protrusion 402 may be tapered radially inward whenextending in a direction toward the bottom of the borehole (andotherwise away from assembly 600). Ultrasonic sensor 438 is mounted tothe front plate 440. Ultrasonic sensor 438 can be used for in-air andnon-contact object detection that detect objects within a defined area.

The ultrasonic penetrometer 218 measures the stiffness and sedimentthickness of the bottom surface of the borehole using, for example, acone shaped protrusion 402, a sensor block 406 coupled to a spring(biasing member) 418 on a sensor rod 412, and a measurement scale 404.The ultrasonic penetrometer 218 measures the exact displacement orabsolute position of moving sensor rod 412 connected to spring 418,which is representation of the strength of materials at the bottom ofthe borehole.

The ultrasonic sensor 438 may generate an analog signal proportional tothe distance from ultrasonic sensor or transducer 438 to the sensor rod412. Ultrasonic sensor 438 uses high frequency waves to detect andlocalize sensor rod 412, and measure the time of flight for a wave thathas been transmitted to and reflected back from proximal end 413 ofsensor rod 412. Proximal end 413 thus may be a reflector configured toreflect ultrasound waves back toward ultrasonic sensor 438. The time offlight is the time necessary for the ultrasonic wave to travel to theproximal end 413 of sensor rod 412 from ultrasonic sensor 438, and theback to ultrasonic sensor 438. The measured time of flight may beshorter or longer as the distance to the sensor rod 412 changesaccording to the compression of spring 418. For example, when spring 418is fully compressed (e.g., by a completely rigid borehole bottom), theultrasound wave emitted from ultrasonic sensor 438 may have a relativelyshort time of flight, as compared to when the borehole bottom is soft,and spring 418 is fully extended. In the fully compressed position,proximal end 413 may be disposed closer to ultrasonic sensor 438 thanwhen in the fully extended position. Spring 418 may be biased toward thefully extended position.

In the above illustrated embodiment, the time-of-flight measurementshelp determine sediment thickness of the soil at the bottom of theborehole. The compression of spring 418 reflects the hardness of thesoil at the bottom surface of the borehole experienced by sensor block402. For example, the harder the soil at the bottom surface of theborehole, the more compression that is observed by spring 418. However,if the soil at the bottom surface of the borehole is relatively soft,less compression is observed by spring 418. Therefore, the calculatedtime of flight is relatively low for harder soil compared to softersoil. The measurements obtained are accurate because the movement of theproximal end 413 of sensor rod 412 corresponds exactly to thepenetration of 402 into the bottom of the borehole.

Ultrasonic sensor 438 has better accuracy to make measurementsindependent of material, color, transparency, and texture than othertools used for direct measurements, such as, e.g., infrared sensors fora metal obstacle. Other methods of direct measurements have their ownassociated problems. For example, an LVDT linear position sensor may beimmune to magnetic fields, and its output may vary depending onvibration, altitude, and temperature. A very precise, accurate, andstable voltage source is required in such a system, which makes a systemusing LVDT very costly.

Additionally, measurement scale 404 displays the proportional positionsof the compressed spring 418 and sensor rod 412 from their originalpositions. The position markings on measurement scale 404 may becaptured by the camera assembly 216. The obtained position measurementsmay be used to visually confirm the measurements obtained by ultrasonicsensor 438.

In one embodiment, the ultrasonic penetrometer 218 is capable ofdetermining sediment thickness at the bottom of a borehole based on,e.g., the depth in which rods 214 penetrate the surface.

FIG. 5 is a schematic view of camera assembly 316 of the borescopesystem according to the present disclosure. Camera assembly 316 includesa miniature color or black and white charge coupled (CCD) camera 216with a wide angle (e.g. approximately 180 degrees) lens. In oneembodiment, the width of camera assembly 316, including the miniaturecamera 216, is substantially less than the diameter of the boreholeunder inspection (e.g., a few inches compared to several feet). Camera216 is protected by side plates 504, 506, and 508. These side plates504, 506, and 508 are constructed using a rigid material such as, e.g.,aluminum. It is to be understood, however, that other materials, such asPVC, may be suitable for use in the side plates. For example, oneembodiment of the present disclosure uses an aluminum side platesenclosed in a PVC casing.

The camera assembly 316 also encloses a tilt and pan gear mechanismincluding gears 510 and 512. A system operator controls the tilt and pangear mechanism to rotate camera 216 through a wide range of motion(e.g., 360 degrees in-plane and 180 degrees out-of-plane). Electroniccontrol board 514 controls the tilt and pan gear mechanism and camera216 in response to operator inputs from controller 150 via power unit132 and power-control cable 120 (see also FIG. 1). Electronic controlboard 514 may provide instructions to vertical servo motor 220 (as shownin FIG. 2B) for tilting camera 216 and horizontal servo motor 222 (alsoshown in FIG. 2B) for rotating it. Electronic control board 514 providesservo motors 220 and 222 with electrical control signals in response tooperator inputs from the tilt and pan controllers 152,154 of controller150 (see FIG. 1). In particular, control board 514 includes amicro-controller with an analog-to-digital (ND) converter and a pulsewidth modulation output driver. The micro-controller receives analoginput signals from tilt and pan controllers 152, 154 and converts thereceived signals to pulse width modulated output signals for accuratelycontrolling the position of servo motors 220 and 222 using control anddriver techniques that are known in the art.

The functionality of the tilt and pan gear mechanism may be furtherdescribed by reference to the vertical servo motor 220 and thehorizontal servo motor 222. The tilt mechanism and vertical servo motor220 constitute a first rotational motion stage for rotating camera 216in a plane defined by vertical axis 224 relative to the observationchamber 206, i.e., tilting camera 216 up to approximately 180 degrees(±90 degrees), as camera 216 is suspended in the borehole. Likewise, thepan mechanism and horizontal servo motor 222 constitute a secondrotational motion stage for rotating camera 216 about vertical axis 224over approximately 360 degrees as camera 216 is suspended in theborehole. By manipulating tilt and pan gear mechanism, also referred toas a motion control mechanism, the operator can control and direct acamera viewing angle or line of sight, which in turn enables theoperator specify areas of the borehole for viewing and inspection.

Referring back to FIG. 4B, an abrasion resistant transparent dome 436provides camera 216 with viewing access while protecting the camera 216from possible damage due to contact with the surfaces being inspected.Although the transparent dome 436 in the embodiment illustrated in FIG.4B is constructed of plastic, any number of transparent materials couldbe used with the borescope system of the present disclosure. The camera216 is further configured by the operator to zoom and focusautomatically while taking images. The camera is also controlled by thesystem operator for zooming in/out and manipulating focus wirelessly inreal-time.

In an alternative embodiment, FIG. 6A depicts a camera assembly 600having two cameras (216 and 604). The second camera 604 may besubstantially similar to camera 216 set forth above with respect toFIGS. 2B and 2C. In some examples, cameras 216 and 604 may be used incombination to capture images and videos of the bottom of the boreholeand the sides of the borehole. For example, camera 216 may be used tocapture images of the bottom and sides of the borehole, or of only thebottom of the borehole. In the example where camera 216 is configured tocapture images of only the bottom of the borehole (and not the sides ofthe borehole), In other examples, the first camera 216 may still becontrolled by the servo motors (220 and 222 described with respect toFIG. 2B). Motor 222, which is used to rotate camera 216 about axis 224by rotating shaft 605, also may control the rotation of camera 604 aboutaxis 224, providing both cameras 216 and 604 with 360 degree viewingcapability. Thus, the rotation of shaft 605 may simultaneously rotateboth cameras 216 and 604. It is also contemplated that a separate motor(not shown) may rotate camera 604 about axis 224.

Assembly 204 may be substantially similar in this embodiment asdescribed above with respect to FIG. 2B, except that in a dual-cameraarrangement, assembly 204 may be lengthened to include a transparentviewing section 602 through which second camera 604 may view the sidesof a borehole. Thus, second camera 604 may visualize a field of viewexterior to assembly 600 through viewing section 602. Viewing section602 may circumferentially enclose a volume within assembly 204 wheresecond camera 604 and stepper motor 602 are located. Viewing section 602may include substantially transparent materials, including, e.g.,tempered glass or a transparent polymer.

Additionally, an expandable member 609 may be coupled to an outercircumferential surface of the dual camera assembly 600 by a transparentframe 614 (shown in 7. 6B and 6C) to help provide second camera 604 withclear view of the sides of a bore. Frame 614 may include a sleeve thatslides over the housing of assembly 600 and may be secured to thehousing while expandable member 609 is aligned over at least a portionof viewing section 602. Expandable member 609 may be an inflatable orotherwise expandable transparent member including an expandable sleeve610 and a support 612. Support 612 may be disposed at a radiallyoutermost portion of sleeve 610, and includes an opening 614. Expandablemember 609 may be inflated by air, water, or another suitable materialdelivered via a source at ground level through a suitable line orconduit (e.g., fluid source 175). Expandable member 609 may be inflatedor expanded before or after assembly 600 is lowered into a borehole. Inuse, an operator may position assembly 600 so that support 612 andopening 614 is adjacent to and/or in contact with a side surface 650 ofa borehole (as shown in FIG. 6D). Support 612 and other outer surfacesof expandable member 609 may include a reinforcing material, e.g., aclear plastic, to help prevent puncture of expandable member 609 duringcontact with the side surface of the borehole. Support 612 may bepositioned around a depression 652 in the side surface 650 of theborehole, forming a partial seal around depression 652. The fluid fromfluid source 175 that inflates expandable member 609 also may flushfluid and debris from depression 652 to enable viewing of depression 652by camera 604. In other words, second camera 604 may visualize a fieldof view exterior to assembly 600 through opening 614, support 612, andsleeve 610. In some examples, expandable member 609 may extend aroundonly a portion of the circumference of assembly 204 (as shown in FIG.6B), while in other examples, expandable member 609 may extend around anentirety of the circumference of assembly 204. When expandable member609 extends around only a perimeter of assembly 204, expandable member609 may be fixed relative to assembly 204, or may be rotatable aroundassembly 204. When expandable member 609 is fixed relative to assembly204, an entirety of assembly 600 may be rotated to enable a 360 degreeview of the borehole. However, when expandable member 609 is rotatablerelative to assembly 204, the entirety of assembly 600 need not beconfigured to rotate within the borehole. Rotation of expandable member609 relative to assembly 204 may be achieved via, e.g., one or moremotors, rails, tracks, and the like.

FIG. 7A and 7B depict a profiling assembly 700 for profiling a borehole.Typically, a foundation bore 701 is roughly in a cylindrical shape.Measuring the actual volume of the bore may not be possible when thebore is filled with slurry and mud.

In general, there are three commonly used types of sensors (ultrasonic,infrared, and laser) for single ended non-contact distance measurement.These sensors measure distance according to a transmitting energy anddeducing parameters based on the reflected energy from an obstacle. In aborehole, the distance to the inner wall may need to be measured atvarious levels along the length of the bore. The medium between thedevice and the bore wall can be either air or bentonite slurry/water.The laser-based distance measurement sensor may not be used because thebentonite slurry is usually opaque (which may interfere with the path ofthe laser). Infrared waves may not be suitable for long-range underwatermeasurement as they may be heavily absorbed in water. Furthermore, thediameter of the bore may vary between 1 m and 3 m. Most of the infraredsensors available have a range of about 120 cm, whereas the borediameter can be as high as 3 m.

In contrast, ultrasonic sensors may have the ability to travel throughopaque media, including, e.g., bentonite slurry and water. Also,ultrasonic sensors have been effectively used for SONAR and can measurehigher distances. Thus, an ultrasonic sensor 706 may be used inprofiling assembly 700 to help determine a profile of a borehole.

The profiling assembly 700 may compute a volume of bore 701 and providea 3D-profile of the bore using a non-contact technique. An actuatingmechanism 710 allows the sensor to profile the entire circumference ofthe bore in situations where the characteristics (e.g., density,temperature, viscosity etc.) of the medium vary to a great extent.Actuating mechanism 710 may include controllers, motors, and the like,which may help rotate ultrasonic sensor 706, enabling ultrasonic sensor706 to survey an entire circumference of a respective borehole. Tomeasure the actual volume of a bore, the volume of the bore is splitinto a set of segments, and the radius of each segment is measured tocalculate the respective segment volume. The data received fromprofiling assembly 700 is used to develop a three dimensional model ofthe bore to help the operator visualize the borehole on a display.

In the above-illustrated embodiment, a microcontroller is used forcontrolling motor that operates the ultrasonic sensor 706. To find aradius 702, the distance between the center of bore and wall of bore isneeded. Ultrasonic sensor 706 generates an analog signal proportional tothe distance between the center and side of the bore. An analog inputpin in the microcontroller receives the analog signal from ultrasonicsensor 706 and gives the distance between sensor and side of bore incentimeters or another suitable dimension. To measure the radius ofvarious segments, the ultrasonic sensor 706 needs to be rotated at eachlevel across the entire bore, for which a stepper motor is used, whichin turn controlled by the microcontroller. A digital pulse with aspecific pattern is generated using the microcontroller, and sent asoutput to control the stepper motor. Ultrasonic sensor 706 is mounted onthe stepper motor shaft, and may be controlled to make distancemeasurements in each step of motor for one complete rotation.

In addition, a depth sensor (e.g., a depth wheel provision) provides theheight of each level where measurements are taken. This process isrepeated at different depths of the bore across its total height, todetermine an approximate total volume of bore. The sensor assembly 700is lowered into the bore at fixed intervals of height (h) (e.g., atvarious levels across bore), as determined by the operator by means of adepth sensor. Based on the intervals, and the overall depth (H), thebore will be divided into n vertical steps/levels. At each step/level,the radial profile will be measured by ultrasonic sensor 706. Theapproximate volume of the bore is computed according to the combinedknowledge of radial profile and the depth (H). It is furthercontemplated that one or more portions of profiling assembly 700 may becoupled to assembly 100 or assembly 600. For example, sensor 706 may bedisposed on a rotatable shaft that extends exterior to cover assembly202. Alternatively, sensor 706 may be disposed on shaft 605. In thisalternative embodiment, the outer housing may include an opencircumferential portion to enable sensor 706 to direct ultrasound wavesto the sides of the borehole.

Profiling assembly 700 may be used even when the medium within theborehole changes with depth. Non-contact measurement techniques have aninherent dependency on the medium in which they operate. Ultrasoundtravels through different mediums at different velocity due to number offactors such as density, temperature, etc. Also, the attenuation ofultrasound varies in each medium. Typically, the medium of the borevaries across the height of the bore (e.g., the bore may be completelyempty or may be filled with fluid at various depths). When the devicemoves from one medium to another, (e.g., air to slurry), the mediumchange may be sensed by observing distance values. For example, thespeed of sound in water is about five times the speed of sound in air.There may be a substantial variation in the distance measured from thesensor 706 when there is a change in medium. Accordingly, thisinformation is used to identify the change in medium.

In order to negate the effect of the medium change, ultrasonic sensor706 may need to be calibrated for each medium in order to obtainreliable distance measurements. The below-explained calibrationtechnique may eliminate the need for calibrating the sensor fordifferent mediums, and identifies the true distance without the need toknow the actual medium. This calibration technique is primarily based onanalysis and rectification of error based on known factors. For example,two measurements are taken for an object by positioning a sensor awayfrom the object at two different locations but separated by a knownoffset between them.

Let D cm be the actual distance from A to B. Let M1 be the firstdistance measurement taken from point A to B. Let M2 be anothermeasurement, taken from point A′ to B, while A′ is situated at an offsetdistance of L cm from A.

From the above statements we know that,

(M1M2) K=L; and

${K = \frac{L}{{M\; 1} - {M\; 2}}};$

To find the true distance D, we use the equation:

D=M1*K.

By identifying the K, it is possible to approximate the actual distancevalue. In a yet another embodiment, M1 and M2 measurements can also besimultaneously taken, by positioning two ultrasonic sensors separated byknown offset L cm. This will minimize time taken for measurement. Theprofiling assembly 700 may include two ultrasonic sensors in order toperform the above-explained calibration, and to minimize the time takenfor measurement. It may be necessary for the ultrasonic sensor 706 to befree from obstacles while measuring and rotating. Additionally, it maybe important to keep profiling assembly 700 waterproof, while allowingthe ultrasonic sensor 706 to rotate freely. The experimental validationmay be performed by completely submerging the sensor in water or othermedium like slurry as well.

FIG. 7C depicts a 3D visualization of a borehole. The 3D plot may beautomatically generated as the ultrasonic sensor 706 measurescircumference of the borehole at different depths.

The system operator may select a 3D plot option on a profiling userinterface (UI) to view the 3D plot of borehole. The 3D plot can beexpanded for a better viewing experience.

EXAMPLE

Experiments were conducted to demonstrate the technique for underwaterdistance measurement. The experiments involved the measurement ofcircumference of an inflatable swimming pool filled with water, ofcontrolled circumference. An inflatable swimming pool with a diameter of3 m and height of 2 feet was filled with water and a number ofexperiments were performed. The prototype was submerged inside theinflatable pool. After a few minutes in water, it was operated (thesensors were rotated). No leaks were identified, indicating satisfactoryunderwater operation and performance.

In another experiment, the prototype was placed at the center of thepool. The diameter of the empty swimming pool was measured first. Thedevice was made to measure the circumference of the top edge of the poolwhich was above water level. Since the medium of propagation was air, nocalibration was required and the radial profile was obtained directly.While a few random values were obtained in the measured data, theyappeared to be due to misalignment of the sensor and the edge of thepool. Readings taken were compared with actual distance (measured withtape) and were satisfactory.

In another experiment, the prototype was once again completely immersedinside the pool. The prototype was placed at the center of the pool andwas made to measure the distance of a fixed point, i.e., the sensorswere not rotated. Many readings were taken by altering the position ofthe prototype inside the pool. The actual distance (measured with tape)was compared to the reading given by the sensor. The actual distance andthe sensor reading correlated with each other and changed linearly.

In yet another experiment, the prototype was completely submerged insidewater and a profile of the pool was taken. The device was placed at thecenter of the pool and the sensors were rotated to sweep the entirepool. The variation in depth was simulated by changing thecircumferential profile of the inflatable pool after each scan.Subsequently, a large number of readings were taken. The true distancewas also measured at a random location using measuring tape and wascompared to the calibrated sensor results.

Calibration Process

Measured radii from the primary and secondary sensors were compared tocalibrate the prototype. For example, at one data point, r1 (the radiusof the primary sensor) was 34, and r2 (the radius measured by thesecondary sensor) was 31. The known offset between the sensors at thatdata point was 12. The correlation factor was governed by the equationof the known offset, divided by the difference between r1 and r2, whichin the example above is equal to 4. Then, the calculated distance isequal to the correlation factor multiplied by r1, or (4*34=136 cm). Thetrue distance measured was 162 cm. The above variation in calculateddistance and true distance was due to the variation of minimumresolution exhibited by sensor due to difference in medium.

For example, a measurement of 1 cm difference between two locations willbe shown as 1 cm in an air medium, giving a resolution of 1 cm, whereasa 5 cm difference between two locations will be shown only as 1 cm inwater.

In another example, if r1 is 33.5 and r2 is 31, then the correlationfactor is 4.8 (or 12/2.5). In this example, the calculated distance is160.8 cm, which is approximately equal to the true distance value of 162cm.

In some examples, sound may travel about 4.2 to 4.8 times faster inwater than it does in air. As a result, the distance measured in watermay be roughly 1/4.5 times the actual distance. However, if the density,temperature, etc., of the water varies, the above ratio also will vary.That said, by using the calibration technique, it will be possible tomake measurements without any considerations to the change in medium.

Furthermore, many ultrasonic sensors have a finite dead zone. The deadzone of an ultrasonic sensor is the minimum range below which the sensoris unable to measure distance. Ultrasonic sensors also have a maximumrange above which they cannot measure. The resolution of most ultrasonicsensors is defined in air. The resolution of the sensor also changeswith changes in medium. Thus, the effective resolution of an ultrasonicsensor varies drastically when in water. The sensor used for thisprototype (MB7070) had a dead zone of 20 cm, maximum range of 700 cm,and a resolution of 1 cm. All the above values are specified for air.When measuring under water, the dead zone increases to about 100 cm, andthe maximum range to about 3500 cm. However, the resolution of thesensor also deteriorates to about 5 cm. As a result, any distancevariations within 5 cm, inside water, may not be detected.

Also, while performing the calibration routine, the better theresolution of the sensor, the more accurate the results will be.

FIG. 8 illustrates further aspects of the overall borescope systemaccording to the disclosure in which computer 118 cooperates withcontroller 150 and display 110. In operation, a reel motor control 804is responsive to user input via controller 150 for raising or loweringcamera assembly 100 within a borehole under inspection. A cable depthsensor 806 provides information regarding the depth of measurementassembly 100 at any given instant as it drops into the drilled shaft. Inaddition, one or more sensor probes 808 (see FIG. 9) may provideinformation to central processing unit 810 regarding any of a number ofcharacteristics of the borehole. A memory 812 associated with computer118 stores the gathered information in this embodiment of thedisclosure. In an example embodiment, the measurement assembly 100comprises of wireless or Bluetooth transmitter. The measurements fromthe camera and ultrasound sensor are transmitted wirelessly to thecontroller 150 or a computing device (e.g. laptop, tablet) with aBluetooth or wireless receiver.

In other words, FIG. 8 shows the components of a control and displayunit according to embodiments of the disclosure. For example, sensorprobes 808 encompass sensors and measurements shown in FIG. 9, includingload cell 902 (for unit weight and viscosity measurements); thermocouple904 (for temperature measurement); conductivity probe 906 (for electricconductivity measurement of the slurry); pressure gauge 908 (for slurrypressure measurement) and the ultrasonic sensor 910 (for thickness ofthe soil) and ultrasonic sensor 912 (for profiling the borehole). Asshown, the control circuitry of FIG. 9 conditions the sensor signals andprepares them for processing by computer 118. For example, the analogsensor signals are conditioned and then multiplexed by an analogmultiplexer 912 before being converted to digital signals by ananalog/digital converter 914 for processing by computer 118.

Those skilled in the art are familiar with thermocouples and pressuregauges suitable for use with the disclosure. The pressure gauge 908measures pressure on measurement assembly 100 as exerted by the slurryin the borehole and the thermocouple 904 measures temperature of theslurry. The load cell arrangement, including load cell 902, along withthe reel motor control 804 and the cable depth sensor 806 are used tomeasure the unit weight, the viscosity of the slurry, and the depth atwhich the measurements are taken.

FIG. 10 shows an exemplary load cell arrangement including the load cell902 of FIG. 9 for obtaining unit weight and viscosity measurements.Advantageously, the load cell arrangement permits determination of theunit weight and the viscosity of the slurry fluid, at different depths,as a function of the slurry's physical properties. For example,measurement assembly 100 including the fluid chamber (i.e., viewingenvelope 510) has a predetermined specific gravity that ranges from 1 to1.4. Based on the anticipated density of the slurry fluid in theborehole, the camera chamber size 212 can be selected to get the desiredspecific gravity (1 to 1.4). This specific gravity of the borescope isvery important to determine the unit weight and the viscosity of theslurry fluid in the borehole.

The measurement assembly 100, can be lowered in the slurry fluid under asubstantially constant velocity (i.e., a controlled fall). At differentdepth intervals, a control unit at the surface such as computer 118detects its depth and buoyant weight from which the unit weight of theslurry can be determined. A digital readout unit at the surface displaysthe relationship between depths versus unit weight. In one embodiment,load cell 902, according to the arrangement of FIG. 10, determines theweight of measurement assembly 100 and the cable depth sensor 806determines its depth. For example, cable depth sensor 806 comprises anoptical wheel sensor 1002 associated with a cable reel 1004 used forraising and lowering measurement assembly 100 by its umbilical cord 120.

Moreover, the borescope system of the present disclosure providesqualitative as well as quantitative measurements to assist indetermining the amount of sedimentary deposits and contamination in theboreholes rather than relying on the personal judgment of the drilledshaft inspector. When the disclosure is employed using a computer withMPEG or similar capability, the analog video images may be converted todigital images that an inspector or analyst can manipulate using digitalfilters, for example, to extract information that may not be detectablefrom a visual inspection of the shaft surfaces. For example, each pixelin an image would be mapped and given a value based on its opticalcharacteristics. An image processor would then process the pixel data.In an alternative embodiment, a digital video camera may be used thatprovides both a video image as well as digital information regarding theimage. Digital filtering and image processing techniques suitable foruse with the present disclosure are known in the art and need not bedescribed further herein. The digitized images and data can be added toa data base on drilled shaft construction and used to improve existingdesign/construction methods.

In one embodiment, the system comprises a portable inspection unit thatcan be transported and operated by a single inspector. Reconfiguring thebasic unit to accommodate additional inspection sensors is alsocontemplated. Such sensors include probes to obtain soil specimens forfurther inspection, probes to measure penetration resistance of thebottom soil, or ultrasound or similar penetrating sensors to gatherinformation below surficial sediments. These additions are regarded asaccessories and may be added to the basic unit when field conditionsrequire such accessories. Advantageously, such a system provides bothportability and versatility to facilitate the process of shaftinspection in a timely manner. Thus, one or two inspectors can performthe job with great efficiency and without causing delays in theconstruction stage of the drilled shafts. Furthermore, the borescopesystem of the present disclosure is not limited to vertical drilledshafts and may be used to inspect non-vertical shafts by adjusting orsubstituting the structure used to support and/or suspend the camera andhousing into the shaft.

Embodiments of the present disclosure may facilitate a boreholeinspection process, and help avoid the need for deploying humaninspectors into the boreholes. Measurements obtained by the presentdisclosure may help avoid parallax errors resulting from reading a scaleat an angle.

The disclosure incorporates U.S. Pat. Nos. 7,187,784 and 8,169,477 intheir entireties by references.

When introducing elements of the present disclosure or the embodiment(s)thereof, the articles “a,” “an,” “the,” and “said” are intended to meanthat there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.

In view of the above, it will be seen that the several objects of thedisclosure are achieved and other advantageous results attained. Asvarious changes could be made in the above constructions, products, andmethods without departing from the scope of the disclosure, it isintended that all matter contained in the above description and shown inthe accompanying drawings shall be interpreted as illustrative and notin a limiting sense.

We claim:
 1. A borescope, comprising: a housing extending from a firstend toward a second end, the housing including a first transparentviewing section extending circumferentially around a longitudinal axisof the housing and defining an exterior of a portion of the housing; afirst imaging assembly configured to rotate about the longitudinal axisof the housing, and also pivot relative to the longitudinal axis of thehousing; and a second imaging assembly disposed within the housing, thesecond imaging assembly being configured to rotate about thelongitudinal axis of the housing, wherein the second imaging assembly isconfigured to visualize a field of view exterior of the housing throughthe first transparent viewing section.
 2. The borescope of claim 1,further including a shaft extending at least partially through thehousing, wherein the first imaging assembly and the second imagingassembly are both configured to rotate simultaneously about thelongitudinal axis of the housing by rotation of the shaft.
 3. Theborescope of claim 1, further including a transparent observationchamber having a first end disposed at or adjacent to the second end ofthe housing, and extending away from both the first end and the secondend of the housing, toward a second end.
 4. The borescope of claim 1,wherein the second end of the housing is configured to transitionbetween a closed configuration where an exterior of the observationchamber forms a fluid-tight seal around a volume, and an openconfiguration where fluid can move into and out of the observationchamber through the second end.
 5. The borescope of claim 4, furtherincluding one or more rods at or adjacent to the second end of thehousing, wherein: each of the one or more rods extends from the secondend of the housing and away from both the first end and the second endof the housing; and each of the one or more rods includes a plurality ofgraduated markings forming a scale indicative of length, wherein eachscale is visible to the first imaging assembly through the transparentobservation chamber.
 6. The borescope of claim 1, further including anexpandable sleeve coupled to an exterior of the housing, wherein theexpandable sleeve is configured to move from a collapsed position to anexpanded position via application of a fluid through the sleeve.
 7. Theborescope of claim 6, further including a rigid support at a radiallyoutermost portion of the expandable sleeve, the rigid support enclosingan opening through which the fluid can exit the expandable sleeve,wherein the second imaging assembly is configured to visualize a fieldof view exterior of the housing through the opening and the expandablesleeve.
 8. The borescope of claim 7, wherein the expandable sleeve iscoupled to the exterior of the housing by a transparent frame disposedcircumferentially around the housing.
 9. The borescope of claim 6,wherein, in the expanded position, the expandable sleeve extends onlypartially around a circumference of the housing.
 10. The borescope ofclaim 1, further including an ultrasonic sensor at or adjacent to thesecond end of the housing, wherein the ultrasonic sensor is configuredto determine a thickness of sediment disposed at a bottom of a borehole.11. The borescope of claim 1, further including: a first ultrasoundsensor configured to generate ultrasound waves; and a reflector movabletoward and away from the first ultrasound sensor along the longitudinalaxis, or along a first axis parallel to the longitudinal axis, whereinthe reflector is configured to reflect the ultrasound waves generated bythe first ultrasound back toward the first ultrasound sensor, and thefirst ultrasound sensor is configured to determine a time-of-flight fora wave to travel from the first ultrasound sensor to the reflector, andthen back to the first ultrasound sensor.
 12. The borescope of claim 11,wherein: the reflector is movable between a fully compressed positionand a fully extended position; the reflector is disposed closer to thefirst ultrasound sensor when in the fully compressed position than whenin the fully extended position; and the borescope further includes abiasing member configured to bias the reflector toward the fullyextended position.
 13. The borescope of claim 12, further including: arod having a first end and a second end, wherein the reflector isdisposed at the first end of the rod; and a tapered block disposed atthe second end of the rod, wherein the tapered block tapers radiallyinward in a direction away from both the first end and the second end ofthe housing.
 14. The borescope of claim 1, further including: a secondultrasound sensor configured to rotate about the longitudinal axis ofthe housing; and a controller configured to receive measurements fromthe second ultrasound sensor to determine a volume of a borehole inwhich the borescope is located.
 15. The borescope of claim 14, furtherincluding a depth sensor configured to determine a depth of theborescope, wherein the controller is configured to receive measurementsfrom the depth sensor, wherein determination of the volume of theborehole also is based on the measurements from the depth sensor.
 16. Aborescope, comprising: a housing extending from a first end toward asecond end; a first imaging assembly coupled to the housing; a firstultrasound sensor configured to generate ultrasound waves; and areflector movable toward and away from the first ultrasound sensor alonga longitudinal axis, wherein the reflector is configured to reflect theultrasound waves generated by the first ultrasound back toward the firstultrasound sensor, and the first ultrasound sensor is configured todetermine a time-of-flight for a wave to travel from the firstultrasound sensor to the reflector, and then back to the firstultrasound sensor.
 17. The borescope of claim 16, wherein: the reflectoris movable between a fully compressed position and a fully extendedposition; the reflector is disposed closer to the first ultrasoundsensor when in the fully compressed position than when in the fullyextended position; and the borescope further includes a biasing memberconfigured to bias the reflector toward the fully extended position. 18.The borescope of claim 17, further including: a rod having a first endand a second end, wherein the reflector is disposed at the first end ofthe rod; and a tapered block disposed at the second end of the rod,wherein the tapered block tapers radially inward in a direction awayfrom both the first end and the second end of the housing.
 19. Aborescope, comprising: a housing having extending from a first endtoward a second end; a first imaging assembly coupled to the housing; anultrasound sensor configured to rotate about a longitudinal axis of thehousing; and a controller configured to receive measurements from theultrasound sensor to determine a volume of a borehole in which theborescope is located.
 20. The borescope of claim 19, further including adepth sensor configured to determine a depth of the borescope, whereinthe controller is configured to receive measurements from the depthsensor, wherein determination of the volume of the borehole also isbased on the measurements from the depth sensor.